Method and apparatus for reconcentrating hygroscopic liquids



NOV. 19, 1940. c DOWNS ET AL 2,222,561

METHOD AND APPARATUS FOR RECONCEN'IRATING HYGROSCOPI C LIQUIDS Filed May 25, 1937 2 Sheets-Sheet 1 O I 32 22b INVENTORS CHAELES R. DO A N5 II! I! II II II If fl 1| I! II II ll II H II II ll 0 I! H" II II II I! II II H II II "I! I! I! W 1940- c. R. DOWNS ETAL METHOD AND APPARATUS FOR RECONCENTRATING HYGROSCOPIC LIQUIDS Filed May 25, 1937 2 Sheets-Sheet 2 INVENTORS CHARLES E. IOSEPH Patented Nov. 19, 1940 UNITED STATES PATENT OFFICE METHOD AND APPARATUS FOR REOONCEN- 'ma'rme nroaoscorrc uoums Charles R. Downs, Old Greenwich, Conn, and

Joseph W. Spiselman, Mamaroneck, N. Y., assignors, by mesne assignments, to The Calorlder Corporation, Greenwich, Conn., a. corporation oi Connecticut 7 Application May 25, 1937, Serial N 0. 144,630

13 Claims.

This invention relates to a method and apparatus for reconcentrating hygroscopic liquids to be used for the dehumidifying and conditioning described a method and apparatus for dehumidifying air by means of a hygroscopic liquid which flows in a plurality of fine streams or films in contact and concurrent direction with the air I through an extended surface heat exchange unit,

in which heat is simultaneously removed from the air and hygroscopic liquid while moisture and heat are being removed from the air by the hygroscopic liquid.

For a given relative humidity of the air discharged from the dehumidifying apparatus, it is necessary to keep the hygroscopic liquid within definite limits of concentration and it is necessary therefore to periodically or continuously remove from the hygroscopic liquid a portion of the moisture which it has absorbed from the air.

We have also described in the said copending application, the construction of a reconcentrator suitable for removing moisture from the hygroscopic liquid and it is the construction and operation of this reconcentrator which is the subject r matter of the present invention.

in our said copending application as used in con- While the reconcentrator has been described nection with a particular type of dehumidiiying unit. it will be understood that the said reconcentrator maybe used with any type of air conditioning unit employing any suitable hygroscopic liquid.

An object of our invention is to provide a reconcentrating unit which will rapidly remove moisture from a hygroscopic liquid with a mini- -matically to maintain the hygroscopic liquidwithin an airconditioner within definite limits of concentration.

Another object of the invention is to provide a reconcentrating unit for a hygroscopic solution which takes advantage to the fullest extent of heat exchange economy between portions of the solution at difierent temperatures and between the solution and a heating medium and amoisture transporting gas.

Another object of the invention is to continu- 'ously transfer a portion at least of the diluted hygroscopic liquid from an air conditioner to a reconcentrator and transfer the reconcentrated liquid to the air conditioner" at a temperature approximatingthat of the dilute solution.

Another object of the invention is to provide a method of reconcentration of a hygroscopic liquid for dehumidifying air in .which the liquid is simultaneously heated and evaporated in contact with a'moisture carrying gas permitting the treatment of the minimum quantity of liquid per unit of time at a minimum temperature.

Another object of the invention is to provide a method and apparatus for regenerating the odor and moisture absorbing properties of a suspension of a finely divided solid deodorizing agent in a hygroscopic solution. a

While the apparatus and method of the present invention will be described with particular reference to its use as a reconcentrator for hygroscopic salt solutions, it will be apparent to persons skilled in the art that the apparatus may be used emciently for'the evaporation and concentration of various hygroscopic liquids.

In the accompanying drawings which illustrate a preferred form of emobdiment 01' our invention:

Fig. 1 is a sectional view of the reconcentrating apparatus which is the subject matter-of our invention.

Fig. 2 is a sectional view on the line 2-2 of Fig. 1 showing the heat exchange unit ing the hygroscopic liquid. 1

'Flg. 3 is a sectional view'on the line '3-3 of Fig. 1 showing in dotted line the heatexchange members in'the base of the reconcentrator.

Fig. 4 is a sectional view on the line 4-4 of Fig. 1 showing details of the countercurrent fiow oi the incoming and outgoing hygroscopic liquid.

Fig. 5 is a sectional view of one form of pre-" heater for the hygroscopic solution to be recon centrated.

Fig. 6 is a side elevation showing a reconcentrator equipped with gas burners for heating the heat exchange members over which the hygroscopic solution flows.

Fig. '7 is a sectional view through the interior of the gas heated reconcentrator shown in Fig. .6.

In the form of embodiment of our reconcentrator illustrated in Fig. 1, a portion of the hygroscopic liquid, or other liquid to be concentrated, is continuously pumped through the pipe into the bottom of the reconcentrating apparatus 10 where it flows through immersed heat for heatexchange units 2! in which the incoming dilute liquid exchanges heat with the outgoing concentrated liquid and thence through the pipe 22 .to a countercurrent heat exchange unit 23 located in the outlet stack II of the reconcentrator l wherein the incoming dilute solution is heated by the outgoing hot gases from the reconcentrator. From the heat exchange unit 23 the dilute solution flows through the pipe 24 and if desired through a preheater 45 into the upper portion of the reconcentrator II] where it is distributed in a plurality of sprays l2 over a distributing or spreading bed of tower packing,

Raschig rings or the like 30 and thence flows over the heating coils 13, from which it flows downward through a second distributing or spreading bed of tower packing, Raschig rings or the like 26 and thence over a plate 21 and through a hole 210 into a pool 28 .at the bottom of the reconcentrator I0.

In this pool the heated and reconcentrated liquid flows in countercurrent contact. through and around the heat exchangers 2lthrough which the incoming dilute solution is flowing,

'1 and thence out through the pipe 29 to the point where it may be used in a dehumidiflcation unit such as described in our copending application Ser. No. 98,646 or for other purposes.

Air for eilectin reconcentration or evaporation of moisture from the hygroscopic solution is forced by the blower 9 through the duct l4 and reconcentrator l0 where it passes upwardly.

in countercurrent flow through the bed of Raschig rings or tower packing 26 and through heating coils I 3 in contact with the hygroscopic solution flowing down over the heating coils l3 and thence, carrying the moisture removed from the hygroscopic solution and some heat from the coils l3, it passes through the second bed of tower packing or Raschig rings 30 in contact with the solution being sprayed thereover and thence through a spray eliminator 3| and into the stack ll of the reconcentrator.

During the operation of removing moisture from the hygroscopic solution flowing through the reconcentrator I 0, steam or other heating fluid is passed from the pipe 15 through the branch pipes 35 and 36 of the heating coils l3 and return pipes 31 to heat the solution flowing over the heating coils i3 and to also heat the air passing therethrough to thereby raise the temperature of the hygroscopic liquid and theair so that the air removes the desired amount of moisture from the hygroscopic liquid at a temperature below its boiling point.

The heat and moisture exchanges taking ditioning apparatus through the pipe 29 at ap-.

proximately the temperature of the dilute solution coming in through the pipe 20. incoming solution, now warmed, flows to gasliquid countercurrent heat exchange unit 23, located in the air duct from the reconcentrator; Here, the dilute solution is further heated by the exchange of both sensible and-latent heat contained in the air flowing through the outlet The dilute I ing latent heat which was added to the air as evaporated moisture in bed 26 and heating coil l3. Drainage is provided for the moisture condensed on unit 23. v

If further preheating of the solution flowin to the sprays I 2 is desired, steam or other heating fluid may be automatically or manually admitted to the preheater 45, through the inlet 41, which may be automatically controlled by an electrically operated valve 49 to admit or prevent the flow of steam through the preheater. In the preheater the steam surrounds the coil 46 through which the dilute solution flows from the pipe 24. The outlet 48 conducts the condensate out of the preheater.

The dilute solution, now heated to a considerable degree. passes to sprays I2, thence through bed 30 and down on to heating coils l3. Here it is heated indirectly by the heating fluid within coils l3, and. is simultaneously in direct contact with the upwardly flowing stream of air which is also being heated by coils l3. Evaporation of water from the solution takes place by virtue of-the increased moisture vapor pressure of the solution and the simultaneous addition of heat from coils l3. .4

The partially reconcentrated and hot solution then flows from coils l3 into bed 26, wherein further countercurrent direct contact with the air causes adiabatic evaporation to take place giving further reconcentration with cooling of the solution. The temperature of the solution discharging from bed 26 will be in proportion to the wet bulb of the incoming air; the lower the wet bulb the lower the temperature of the solution at that point. The reconcentrated and partially cooled solution then passes to the pool 28 forming part of the liquid-liquid heat exchange unit 2| as previously described to effect the final cooling. By this system 01' heat exchangers a minimum quantity of'solution may be "utilized for reconcentration and the two losses of useful heat, 1. e., the temperature oi. the leaving reconcentrated solution and the total heat of the hot air in outlet stack II, are both reduced to eflect efficient evaporation of moisture from the hygroscopic solution. a I In United States Patent No. 2,027,093 the disclosure is made that foreign, odors present in a moisture absorbing material used either in'the liquid or solid phase maybe removed therefrom by means of. finely divided solid deodotizing agents for example activated carbon. Odors are also removed by this means from air being dehumidified. In copending application Ber. No.

. 98,646, filed August 31, 1936, or which this application is a continuation in part, an improvement is disclosed in that odors are removed from air by suspending activated carbon in thin films of a hygroscopic solution containing activated carbonin suspension and simultaneously dehumidifying and deodorizing the air by contact of thin streams thereof with said thin films of hygroscopic liquid. In that disclosure the odor absorbing properties of the thin films of the suspension are regenerated by the addition of fresh deodorizing agent.

We have since found that by our. method of regenerating thehyg roscopic liquid for absorbing moisture there takes place the regeneration of the odor absorbing properties of the suspension. Although we do not intend to be limited as to a theory of the regeneration of the odor absorbing properties of the suspension, we believe the process may be a reversal of the action which takes place in the dehumidifying apparatus described in our said copending application wherein the hygroscopic liquid containing the carbon in suspension is spread in very thin extended films on the fins of the cooling unit which affords a large surface in contact with the thin streams of air. The intimacy of contact of air and suspension is very great and odoriferous constituents are removed rapidly. Temperature rises of the suspension in that device are limited and its absorptive properties are preserved thereby. In the reconcentrator the suspension is also spread in very thin films, but upon the extended heated surfaces of the coils l3. The heating of the films of the suspension in contact with the heated and unsaturated air passing over these films removes the absorbed odoriferous materials fromthe suspension by vaporizatiomoxidation or a combination of these and other unknown causes. The suspension is thus reactivated and reconcentrated simultaneously for further use.

Control of the flow of steam or other heating fluid through the pipe l and the heating coil l3 and if desired through the preheater 45 may be efiected by means of an electrically operated valve l1 and an electrically operated valve 49 which may be automatically controlled from some remote point, such as an air conditioning unit as described in our said copending application; to automatically start or stop the flow of heating fluid through the heat exchange unit l3 and if desired through the preheater 45 when the concentration of the hygroscopic solution falls below or rises above a predetermined point. Such control may be energized by the air being disportion of a series of pipe coils 40 having heat charged from the air conditioning unit, by the specific gravity of the solution contained therein, by the air in the conditioned space and the like. A suitable fan or blower 9 may be used to force air through the reconcentrating apparatus id to remove and carry away the moisture from the hygroscopic solution when the unit is in operation to reconcentrate the solution and the blower 9 may be likewise automatically started and stopped to effect reconcentration when desired in accordance with the degree of dilution existing in the dehumidifying unit.

The air entering the reconcentrator may be outside unconditioned air, or may be air from the conditioned space. We have taken this amount of air from the conditioned space, and we have found that this amount is closely equivalent to that generally needed for the fresh air requirements for the ventilation of the conditioned space. By providing for such ventilation by this method, we have also found that this afiords a cooler reconcentrated solution to be returned to the air conditioning unit.

When the conditioned space must be continuou'sly ventilated, the air for the reconcentrator is withdrawn from the conditioned space continuously; when the ventilation requirements are not continuous or if outside air isused for reconcentration, the air flow may be in or off as the valve I1 opens or closes.

As shown in Figures 3 and 4, the heated reconcentrated solution which passes through the bed of Raschig rings or tower packing 26, flows down the sloping pan 2! to the hole 21a located at one corner of the pan where it flows into the pool 28 at the bottom of the reconcentrator, which pool of warm reconcentrated hygroscopic liquid surrounds the heat-exchange units 2! into which the cold incoming solution is received from the pipe 20. Baifles 38 in the bottom of the reconcentrator 9 cause the reconcentrated hygro-i scopio solution to flow in tortuous path through the immersed heat exchange units 2i so that the incoming hygroscopic solution is preheated and the outgoing concentrated hygroscopic solution is cooled before it reaches the outlet pipe 29.

When heat is withdrawn from the heated air by the heat exchange unit 23, a substantial quantity of heat'is recovered and by countercurrent flow to the cooler hygroscopic solution passing through the heat exchange unit 23, the temperature of the air is lowered so that a substantial amount of moisture condenses out on the external surfaces of the heat exchanger 23 which moisture is caused to flow into the sump 32 and is discharged through the pipe 33. The water discharged from the pipe 33 is soft water and may be recovered and applied to useful purposes such as make-up water in an evaporative cooler or steam boiler, or the like.

When outside weather conditions are encountered which would cause the air discharged from the stack II to discharge a spray or cloud from the stack, which might be objectionable, the use of the heat exchanger 23 may be discontinued, by closing the valve 22b to divert the incoming solution through the pipe 24a and bypass the heat exchanger 23, so that the gases may pass through the stack i l without having their temperature materially reduced.

Figures 6 and 7 show a particular form of gas fired heat exchange unit or heating coil which may be used in place of the coil l3. In this form of coil, the gases to be burned are forced or aspirated from the header l5a into the lower .charged from the reconcentrator unit, flow through. the stack ll past the heat exchange unit or preheater 23. A substantial recovery of heat from the hot products of combustion is thus obtained and is made useful as heat in the dilute solution passing to sprays l2. The flow of gas through the coils 40 may be automatically controlled by means of an electrically operated valve lla, pilot jets 43 or other suitable means being maintained to ignite the flow of gas when it is As the air and hygroscopic solution flow countercurrent over the heat exchange units I3 and M, the fins l3a and 4| should be spaced suffifrom the hygroscopic solution by the heated air. Y

ciently far apart to prevent flooding of the heat exchange unit.

During operation of the reconcentrator in conjunction with an air conditioning machine, the hygroscopic liquid circulating to the reconcentrator may be stopped or started as valves I! or Ila close or open to admit heating fluid to coils l3 or 40. C011 l3 may be still hot after the liquid ceases to flow and certain solutions under these conditions may continue to concentrate in the thin films clinging to the fins of coil I3 and will crystallize. To avoid such an event we prefer to circulate the hygroscopic solution continuously through the reconcentrator whether the valves I 1 or l'la are open or closed as long as the air conditioner is controlling the conditioned space. The continuous fiow of the solution over coil l3 will prevent crystallization.

It has been our experience that the reconcentrating capacity of the reconcentrator I 0 maybe considerably increased by heating the solution from the gas-liquid heat exchanger 23 to a still higher temperature. This may be done by means of an indirect preheater 45 in line 2| using steam or other heating fiuid as the heating medium. With such preheated solution passing through bed 30, the air temperature leaving bed 30 is considerably increased, and with that its capacity for moisture. This added moisture is evaporated into the air adiabatically in bed 30; the partially cooled solution then fiows to coil l3 to pass through the remainder of the cycle as previously described. This partial cooling of the solution in bed 30 preserves the heating ability of coil I3 to approximately the same extent as it would have without the addition of the preheater 45 in line 24 and the reconcentration capacity of the unit is increased by the evaporation taking place in bed 30.

While we have illustrated and described our invention in connection with the concentration or reconcentration of a hygroscopic salt solution, such as calcium chloride, lithium chloride and the like, suitable for use in the dehumidification of air or the other gases, it will be understood that the apparatus'and method described may be used for the evaporationor removal of moisture from other types of solutions and also that various modifications and changes may be made in the particular form of apparatus herein shown and described without departing from the spirit of our invention or the scope of the appended claims.

We claim: 1. The method of reconcentrating and cooling a diluted hygroscopic solution, which includes distributing said diluted solution in thin films over heated surfaces to heat it and to evaporate some of the moisture, cooling the thereby partially concentrated solution and further concentrating it by passing the heated solution as thin films countercurrent to a stream of unheated air,

- distributing said diluted solution in thin films flowing over heated surfaces to heat-it and to evaporate some' of the moisture, cooling the thereby partially concentrated solution and further concentrating it by passing the heated solution as thin films countercurrent to a stream of unheated air, thereby heating said air and evaporating further moisture from said solution, pass- 4 ing said heated air in a countercurrent direction over the films on said heated surfaces to effect the first -mentionedevaporation, and further cooling the concentrated solution by indirect heat exchange with the diluted solution to be reconcentrated.

3. The method of reconcentrating and cooling a diluted hygroscopic solution, which includes distributing said diluted solution in thin films over heated surfaces to heat it and to evaporate some of the moisture, cooling the thereby partially concentrated solution and further concentrating itby passing the heated solution as thin films countercurrent to a stream of unheated air, thereby heating said air and evaporating further moisture from said solution, passing said heated air in a countercurrent direction over the films on said heated surfaces to effect the first mentioned evaporation, separating the cooled concentrated solution from the incoming unheated air, and preheating the dilute solution delivered to said heated surfaces by passing it in indirect heat exchange relationship with the air leaving said heated surfaces.

4. The method of reconcentrating and cooling a dilute hygroscopic solution, which includes distributing said dilute solution in thin films over heated surfaces to heat it and to evaporate some of the moisture, cooling the thereby partially concentrated solution and further concentrating it by passing the heated solution as thin films countercurrent to a stream of unheated air, thereby heating said air and evaporating further moisture from said solution, passing said heated air in a countercurrent direction over the films on said heated surfaces to effect the first mentioned evaporation, separating the cooled concentrated solution from the incoming unheated air, further cooling the concentrated solution by indirect heat 7 exchange with the diluted solution, and pre-heating the dilute solution delivered to said heated surfaces by passing it in indirect heat exchange relationship with the air leaving said heated surfaces.

5. The method of reconcentrating a hygroscopic salt solution, including delivering the diluted solution in thin films over a heated surface, heating said surface by hot gases of combustion out of contact with the solution, .passing the heated solution as thin films countercurrent to a stream of unheated air, and thereby heating said air, cooling said solution. and evaporating further moisture from said solution, passing said heated air in a countercurrent direction over the films on said heated surface, separating the cooled con centrated solution from the incoming unheated air, and mixing the gases of combustion with the heated moisture laden air leaving said heated surface.

6. The method of reconcentrating a hygroscopic salt solution by the action of heat and a stream of air withdrawn from a conditioned space, which includes distributing the diluted solution in thin filmsover heated surfaces to heat it and to thereby evaporate some 01' the moisture. cooling the thereby partially concentrated solution and further concentrating it by passing the heated solution as thin films countercurrent to said stream of air, thereby heating said air, pass ing said heated air in a countercurrent direction over the films on said heated surfaces, and separating the cooled concentrated solution from the incoming unheated air.

7. An apparatus for evaporating water from diluted hygroscopic solution, comprising a heat exchanger for preheating the diluted solution, an extended surface heating element, elements therebelow presenting extended non-heated surfaces, means for discharging the preheated solution from said heat exchanger over said first mentioned extended surface to form thin films, and thence in heated condition as liquid films over said extended non-heated surfaces, means for passing non-heated air into said apparatus and all of it over the films on said non-heated surface to evaporate water and cool the films, and thence all of it over the films on said heating element'to absorb further water therefrom, and means for delivering the concentrated solution leaving said non-heated surface through said heat exchanger to further cool said concentrated solution.

8. An evaporating apparatus including a source of hygroscopic solution, a casing, an extended surface heating element therein, a tower packing above said element, a tower packing below said element, means for delivering air to said casing solely below said second mentioned tower packing whereby the air passes upwardly throughthe separate towerpackings and intermediate heating element, means for distributing said solution as thin films over the upper tower packing, the heating element, and the lower tower packing, countercurrent to the fiow of said air, and a collecting chamber for receiving the concentrated solution leaving the lower tower packing.

9. The method of producing a cooled, reconcentrated hygroscopic salt solution from a diluted incoming unheated air,,mixing the hot waste combustion gases with the heated moisture laden air leaving the heated surface, and preheating the I diluted solution delivered to the heated surface by passing it in indirect heat exchange relationship with the air leaving the heated surface and the regenerate the odor-absorbing properties of said I carbon, cooling the thereby partially concentrated and regenerated solution and further concentrating it,by passing the heated solution as thin films in contact with and countercurrent to a stream of unheated air, thereby heating said air and evaporating further moisture from said solution, passing said heated air in a countercurrent direction over the films on said heated surfaces to effect the first mentioned evaporation, and withdrawing the cooled concentrated and regenerated solution.

11. The method of simultaneously evaporating water from and regenerating the odor-absorbing properties of a suspension of finely divided activated carbon in a diluted hygroscopicsalt solution, which includes flowing said suspension in thin films over heated surfaces whereby said films are heated, cooling the heated solution by passing it as further thin films out of contact with said heating surfaces, passing unheated air countercurrent to said last mentioned films to evaporate moisture from the heated solution and to heat said air, and passing said heated air countercurrent to said ilrstimentioned films to evaporate moisture therefrom while the films are being heated.

12. An evaporating apparatus comprising a source of dilute hygroscopic solution, a heat exchanger for preheating said dilute solution, an extended surface heating element, elements therebelowipresentlng extended non-heated surfaces, means to discharge the preheated solutionfrom said heat exchanger over, said first mentioned element to form thin films and thence all of it in heated condition in thin films over said extended non-heated surfaces, a source of air of reduced dew point, and means for passing all of said air from said last mentioned source upwardly over the films on said non-heated surfaces to g evaporate water and cool the films and thence all of said air over the films on said heating elemen to absorb further water therefrom.

13. The method of concentrating and cooling a diluted hygroscopic solution which includes distributing said diluted solution in thin films, successively over unheated surfaces and heated surfaces to evaporate some of the moisture, cooling the thereby partially concentrated solution and further concentrating it by passing the heated 50 solution as thin films countercurrent to a stream of unheated air. thereby heating said air and evaporating further moisture from said solution and cooling the same, passing said heated air in a countercurrent direction successively over the films on said heated and unheated surfaces to effect the first mentioned evaporation and withdrawing the cooled concentrated solution.

CHARLES R. DOWNS. JOSEPH W. SPISEIMAN. 

